Hi,
From the Followups page for the list, you can click "Reset Users" at the bottom of the followup listing which will display entry fields where you can choose a new sequence and delay for all users on the list.
If you only want to change those on sequence 1 to sequence 2 you will need to use a custom MySQL command from phpMyAdmin, commonly available through your web hosting control panel. To update users on list 389, sequence 1 to sequence 2, delay 0, login to phpMyAdmin, choose the ListMailPRO database in the left menu, click "SQL" near the top and enter:
update lm_users set cseq = '2', cdel = '0' where list = '389' and cseq = '1';
Regards